Abstract: In this study, efficient preconcentration method has been developed for the determination of 2,4-dichlorophenoxyacetic acid (2,4-D) using biosorption based on microassemblies combined with core-shell magnetic molecularly imprinted polymers (mag-MIP) nanoparticles followed by high-performance liquid chromatography. The method involves three steps: (1) The bioaggregates is added to the sample. The analyte is extracted into the colloidal phase formed by aggregation of the rhamnolipid. (2) Mag-MIPs are added in order to selectively extract 2,4-D from the bioaggregate. (3) The mag-MIPs are then collected from the solution by a strong magnet placed underneath the test tube, and 2,4-D is desorbed from the surface of the mag-MIP with an acetonitrile: methanol mixture. This material has a high adsorption capacity and yields high upconcentrations, which is reusable and chemically stable. Under optimum conditions, the enrichment factor was 265. The linear dynamic range and limit of detection are 0.16-40 and 0.053 μg L-1, respectively. The relative standard deviations for six replicate measurements are 5.2 %Template and target information:2,4-dichlorophenoxyacetic acid, 2,4-DAuthor keywords:Rhamnolipid, Aggregation, magnetic nanoparticles, Silica coating, HPLC